Hydraulic Drive System

ABSTRACT

A hydraulic drive system is provided and generally includes a first rotor assembly arranged along a first side of the frame and having a first rotor and a first drive shaft extending through and connectable with the first rotor, a first motor assembly disposed along the first side of the frame and positioned linearly the first rotor assembly and a second rotor assembly arranged along a second side of the frame that is opposite the first side and having a second rotor and a second drive shaft extending through and connectable with the second rotor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/402,674, filed Jan. 10, 2017, claiming priority under 35 U.S.C. §119.

FIELD OF THE INVENTION

The present invention relates to a hydraulic drive system, and moreparticularly, to a hydraulic drive system powering drive wheels of aself-propelled trailer.

BACKGROUND

Hydraulic drive systems providing motive power in various applications,including providing power to drive wheels, are known in the art. Invarious applications, known hydraulic drive systems, used power drivewheels, have one or more hydraulic motors that continually connected andengaged with each drive wheel.

Many hydraulic drive system applications do not require the hydraulicmotors to always provide the motive power, and consequently, thehydraulic motors are disengaged when not in use to prevent a resistancethat slows the drive wheel and decreases the useful life of thehydraulic motor. However, known hydraulic drive systems are difficult todisengage and are disengaged manually. Known hydraulic drive systemsthus decrease efficiency by not permitting simple engagement anddisengagement, and by not optimally engaging and disengaging drivewheels depending on the required use of the hydraulic motors.

SUMMARY

An object of the invention, among others, is to provide a hydraulicdrive system capable of engaging and disengaging drive wheels.Accordingly, a hydraulic drive system according to the invention isprovided. The hydraulic drive system includes a first rotor assemblyarranged along a first side of the frame and having a first rotor and afirst drive shaft extending through and connectable with the firstrotor, a first motor assembly disposed along the first side of the frameand positioned linearly the first rotor assembly and a second rotorassembly arranged along a second side of the frame that is opposite thefirst side and having a second rotor and a second drive shaft extendingthrough and connectable with the second rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference tothe accompanying figures, of which:

FIG. 1 is a perspective view of a trailer and a hydraulic drive systemaccording to the invention;

FIG. 2 is a perspective view of a hydraulic drive system according tothe invention;

FIG. 3 is a partial sectional view of the hydraulic drive system of FIG.2;

FIG. 4 is an exploded view of a motor assembly, a rotor assembly, and abody housing of the hydraulic drive system of FIG. 2;

FIG. 5 is an exploded view of the motor assembly of FIG. 3;

FIG. 6 is an exploded view of a motor actuator of the motor assembly ofFIG. 3;

FIG. 7 is an exploded view of the rotor assembly of FIG. 4;

FIG. 8 is an exploded view of a hub assembly of the rotor assembly ofFIG. 4;

FIG. 9 is an exploded view of a rotor actuator assembly of the rotorassembly of FIG. 4;

FIG. 10 is an exploded view of a lever assembly of the hydraulic drivesystem of FIG. 1;

FIG. 11 is a partial sectional view of the hydraulic drive system ofFIG. 1, showing one half thereof;

FIG. 12 is a sectional view of a lever assembly for the hydraulic drivesystem of FIG. 10;

FIG. 13 is a perspective view of the lever assembly for the hydraulicdrive system of FIG. 10;

FIG. 14 is top plan view of the hydraulic drive system of FIG. 1 in anengagement position;

FIG. 15 is a top plan view of the hydraulic drive system of FIG. 1 in adisengagement position;

FIG. 16 is a perspective view of a rotor actuator and a motor actuatorof the hydraulic drive system of FIG. 1;

FIG. 17 is a sectional view of the hydraulic drive system of FIG. 1 inthe engagement position; and

FIG. 18 is a sectional view of the hydraulic drive system of FIG. 1 inthe disengagement position.

FIG. 19 is a partial sectional view of the hydraulic drive system ofFIG. 2;

FIG. 20 is an exploded view of a motor assembly, a rotor assembly, and abody housing of the hydraulic drive system of FIG. 2;

FIG. 21 is an exploded view of the motor assembly of FIG. 19;

FIG. 22 is an exploded view of a motor actuator of the motor assembly ofFIG. 19;

FIG. 23 is an exploded view of the rotor assembly of FIG. 20;

FIG. 24 is an exploded view of a hub assembly of the rotor assembly ofFIG. 20;

FIG. 25 is an exploded view of a rotor actuator assembly of the rotorassembly of FIG. 20;

FIG. 26 is an exploded view of a lever assembly of the hydraulic drivesystem of FIG. 1;

FIG. 27 is a partial sectional view of the hydraulic drive system ofFIG. 1, showing one half thereof;

FIG. 28 is a sectional view of a lever assembly for the hydraulic drivesystem of FIG. 26;

FIG. 29 is a perspective view of the lever assembly for the hydraulicdrive system of FIG. 26;

FIG. 30 is top plan view of the hydraulic drive system of FIG. 1 in anengagement position;

FIG. 31 is a top plan view of the hydraulic drive system of FIG. 1 in adisengagement position;

FIG. 32 is a perspective view of a rotor actuator and a motor actuatorof the hydraulic drive system of FIG. 1;

FIG. 33 is a sectional view of the hydraulic drive system of FIG. 1 inthe engagement position; and

FIG. 34 is a sectional view of the hydraulic drive system of FIG. 1 inthe disengagement position.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

The invention is explained in greater detail below with reference toexemplary embodiments of a hydraulic drive system according to theinvention. However, this invention may be embodied in many differentforms and should not be construed as limited to the embodiments setforth herein; rather, these embodiments are provided so that thisdisclosure will be thorough and complete and still fully convey thescope of the invention to those skilled in the art.

With respect to FIG. 1, a hydraulic drive system 1 according to theinvention is shown. In an exemplary embodiment of the invention, thehydraulic drive system 1 according to the invention is shown with aframe 910, a fluid supply system 920, an engagement mechanism 930, apair of drive wheels 940, and a pair of steerable wheels 950.

With respect to FIG. 2, the hydraulic drive system 1 according to theinvention is shown in greater detail. The hydraulic drive system 1includes the following major components: a body housing 100, a fluidline assembly 200, a first motor assembly 300, a second motor assembly400, a first rotor assembly 500, a second rotor assembly 600, and anengagement assembly 700.

A plurality of fasteners 800 are shown in the figures and describedbelow. It should be known to one skilled in the art that the fastener800 may be a screw, a nut and bolt, a pin and clip, an adhesive, a weld,or any other type of fastener known to those with ordinary skill in theart.

As shown, the hydraulic drive system 1 is symmetrical about an axis A-Ashown in FIG. 2. The following description of the hydraulic drive system1 will reference figures depicting a first half of the hydraulic drivesystem 1, on one side of the symmetrical axis A-A. Components of anopposite second half of the hydraulic drive system 1 will be describedsimilarly to those on the first half, and are shown in the FIGS. 2,19-34. The components of the symmetrical second half of the hydraulicdrive system 1 are identical to those depicted in the figures for thefirst half.

The body housing 100 is shown in FIGS. 2, 19 and 20. In the shownembodiment, the body housing 100 is a hollow cylindrical member having afirst flange 110 at a first end and a second flange 120 at second endpositioned opposite the first end. The body housing 100 also has aplurality of fluid line ports 130 disposed on and extending through aside of the body housing 100.

The fluid line assembly 200 includes a plurality of exterior lines 210,212, a plurality of wall connectors 214, 216, a plurality of interiorlines 220, 222, 230, 232, and a plurality of interior couplings 240,242, 250, 252. The plurality of exterior lines 210, 212 and plurality ofinterior lines 220, 222, 230, 232 may be any type of hydraulic fluidline known to those with ordinary skill in the art. The fluid lineassembly 200 of one half of the hydraulic drive system 1 are shown inFIGS. 2-4 and the second half is shown in FIGS. 2, 19-20.

As shown in FIG. 2, the exterior lines 210 include two pairs of fluidlines 210 a and 210 b, for intake and outlet of fluid. While a total offour exterior lines 210, in an alternative embodiment, the exteriorlines 210 may be replaced by a single pair of fluid lines 210 a and 210b.

As shown in FIG. 3, a plurality of first wall connectors 214 areconnected at a first end to the plurality of first exterior lines 210and connected at an opposite second end to a first interior line 220 anda second interior line 222.

As shown in FIGS. 3 and 4, the first interior line 220 is connected to afirst interior coupling 240 at an end opposite the first wall connector214, and the second interior line 222 is connected to a second interiorcoupling 242 at an end opposite the first wall connector 214.

As shown in FIGS. 2, 14, 15, 19, 27, 30 and 31, a plurality of secondexterior lines 212 includes two fluid lines 212 a and 212 b. In analternative embodiment, the plurality of second exterior lines 212 maybe replaced by a single exterior line 212.

A plurality of second wall connectors 216 are connected at a first endto the plurality of second exterior lines 212 and are connected at anopposite second end to a third interior line 230 and a fourth interiorline 232. In the alternative embodiment described above, in which theplurality of second exterior lines 212 are replaced by a single exteriorline 212, one second wall connector 216 connects at a first end to thesecond exterior line 212 and is connected at an opposite second end tothe third interior line 230 and the fourth interior line 232.

The third interior line 230 is connected to a third interior coupling250 at an end opposite the second wall connector 216, and the fourthinterior line 232 is connected to a fourth interior coupling 252 at anend opposite the second wall connector 216.

The first motor assembly 300 is shown in FIGS. 3-5. As shown in FIG. 5,the first motor assembly 300 includes a first motor 310, a first motoradaptor 320, a first planetary gear drive 330, and a first motoractuator 340.

The first motor 310, as shown in FIG. 5, is a hydraulic motor having afirst motor shaft 316 operated by the hydraulic motor. The first motor310 also has a plurality of first motor couplings 312, 314. The firstmotor adaptor 320, in the shown embodiment, is a hollow cylindricalmember. The first planetary gear drive 330 is a type of planetary gearknown to those with ordinary skill in the art, and has a first planetarymating spline 332 extending into a side of the first planetary geardrive 330.

As shown in FIGS. 5 and 6, the first motor actuator 340 has a firstmotor actuator mating spline 342 disposed on a first end, a plurality offirst motor actuator teeth 346 disposed on an opposite second end, and aplurality of first motor actuator ridges 344 disposed between the firstend and the second end. The first motor actuator mating spline 342, inthe shown embodiment, extends along a longitudinal direction of thefirst motor actuator 340. The plurality of first motor actuator ridges344 protrude circumferentially from the first motor actuator 340.

The plurality of first motor actuator teeth 346 protrude from the firstmotor actuator 340 in the longitudinal direction of the first motoractuator 340.

As shown in FIGS. 19-21, the second motor assembly 400 includes a secondmotor 410, a second motor adaptor 420, a second planetary gear drive430, and a second motor actuator 440.

The second motor 410, as shown in FIG. 21, is a hydraulic motor having asecond motor shaft 416 operated by the hydraulic motor. The second motor410 also has a plurality of second motor couplings 412, 414. The secondmotor adaptor 420 is a hollow cylindrical member. The second planetarygear drive 430 is a type of planetary gear known to those with ordinaryskill in the art, and has a second planetary mating spline 432 extendinginto a side of the second planetary gear drive 430.

As shown in FIGS. 21 and 22, the second motor actuator 440 has a secondmotor actuator mating spline 442 disposed on a first end, a plurality ofsecond motor actuator teeth 446 disposed on an opposite second end, anda plurality of second motor actuator ridges 444 disposed between thefirst end and the second end. The second motor actuator mating spline442 extends along a longitudinal direction of the second motor actuator440. The plurality of second motor actuator ridges 444 protrudecircumferentially from the second motor actuator 440. The plurality ofsecond motor actuator teeth 446 protrude from the second motor actuator440 in the longitudinal direction of the second motor actuator 440.

The first rotor assembly 500 is shown in FIGS. 2 and 7-9. The firstrotor assembly 500 includes a first bell housing 510, a first rotor 530,a first brake 540, a first hub assembly 550, a first drive shaft 570,and a first rotor actuator assembly 580.

The first bell housing 510, as shown in FIGS. 7 and 9, is a bell-shapedmember defining a first bell housing receiving space 511 and having afirst bell housing flange 512 along a first end thereof. A first shaftreceiving passageway 514 extends through the first bell housing 510 in adirection orthogonal to an axis B-B extending through the first bellhousing receiving space 511. The first shaft receiving passageway 514 ispositioned toward a side, off-center on the first bell housing 510. Atubular first caster housing 516 extends from the first bell housing510. A first frame support 518 is disposed around the first casterhousing 516, forming flat surfaces on a top and a bottom of the firstcaster housing 516. As shown in FIG. 8, a first brake mount 520 isdisposed on an end of the first caster housing 516 opposite the firstbell housing 510, and extends away from the first caster housing 516.

The first rotor 530 is shown in FIG. 7. The first rotor 530 may be anytype of brake rotor known to those with ordinary skill in the art.

The first brake 540 is shown in FIG. 7 and includes a first brakecaliper 542 and a plurality of first brake pads 544 disposed within thefirst brake caliper 542. The first brake caliper 542 and the pluralityof first brake pads 544 may be any type of brake caliper and brake padsknown to those with ordinary skill in the art.

The first hub assembly 550 is shown in FIGS. 7 and 8. The first hubassembly 550 includes a first hub housing 552, a first spindle 554, afirst inner hub bearing 556, a first outer hub bearing 558, a first hubring 560, and a first hub retainer 562.

The first hub housing 552, as shown in FIG. 8, has a circular first hubhousing base 552 a and a hollow, cylindrical first hub housing body 552extending from a side of the first hub housing base 552 a.

The first spindle 554, as shown in FIG. 8, is a substantially tubularmember having a first spindle end 554 a at a first end and a firstspindle securing end 554 e at an opposite second end. The first spindlesecuring end 554 e may have an exterior thread, as in the shownembodiment. The first spindle 554 also has a first spindle groove 554 b,a first spindle ridge 554 c, and a first outer spindle surface 554 ddisposed between the first end and the second end. The first spindlegroove 554 b is a groove extending circumferentially around the firstspindle 554 adjacent the first end. The first spindle ridge 554 cprotrudes circumferentially around the first spindle 554 and is disposedbetween the first spindle groove 554 b and the first spindle securingend 554 e. The first outer spindle surface 554 d is a flat surfaceformed orthogonal to a longitudinal direction of the first spindle 554and extending circumferentially around the first spindle 554. The firstouter spindle surface 554 d is disposed between the first spindle ridge554 c and the first spindle securing end 554 e.

The first inner hub bearing 556 and the first outer hub bearing 558, asshown in FIG. 8, may be any form of bearing known to those with ordinaryskill in the art. The first hub ring 560 is a circular member. The firsthub retainer 562 may be a threaded nut, or may be any other form ofretainer known to those with ordinary skill in the art.

The first drive shaft 570 is shown in FIG. 7. The first drive shaft 570has a first drive shaft flange 572 disposed on a first end and a firstdrive shaft spline 576 disposed on an opposite second end. A first driveshaft body 574 is a cylindrical member extending between the first driveshaft flange 572 and the first drive shaft spline 576.

The first rotor actuator assembly 580 is shown in FIG. 9. The firstrotor actuator assembly 580 has a first rotor actuator 582, a pluralityof first rotor actuator bearings 590, and a first rotor actuator snapring 592. The first rotor actuator 582 has a plurality of first rotoractuator teeth 584 disposed on a first end thereof, a first rotoractuator mating end 586 at an opposite second end thereof, and a firstrotor actuator spline 588 disposed along an interior of the first rotoractuator 582. The plurality of first rotor actuator teeth 584 protrudefrom the first rotor actuator 582 in a longitudinal direction of thefirst rotor actuator 582. The first rotor actuator spline 588 extendsalong the longitudinal direction of the first rotor actuator 582. Thefirst rotor actuator mating end 586 may have an exterior thread, as inthe shown embodiment. The plurality of first rotor actuator bearings 590may be any type of bearings known to those with ordinary skill in theart. The first actuator snap ring 592 may be any type of snap ring knownto those with ordinary skill in the art.

The second rotor assembly 600 is shown in FIGS. 2 and 23-25, includes asecond bell housing 610, a second rotor 630, a second brake 640, asecond hub assembly 650, a second drive shaft 670, and a second rotoractuator assembly 680.

The second bell housing 610, as shown in FIGS. 23 and 25, is abell-shaped member defining a second bell housing receiving space 611and having a second bell housing flange 612 at a first end. A secondshaft receiving passageway 614 extends through the second bell housing610 in a direction orthogonal to an axis B-B extending through thesecond bell housing receiving space 611. The second shaft receivingpassageway 614 is positioned toward a side, off-center on the secondbell housing 610. A tubular second caster housing 616 extends from thesecond bell housing 610. A second frame support 618 is disposed aroundthe second caster housing 616, forming flat surfaces on a top and abottom of the second caster housing 616. A second brake mount 620 isdisposed on an end of the second caster housing 616 opposite the secondbell housing 610, and extends away from the second caster housing 616.

The second rotor 630 is shown in FIG. 23 and may be any type of brakerotor known to those with ordinary skill in the art.

The second brake 640 is shown in FIG. 23 includes a second brake caliper642 and a plurality of second brake pads 644 disposed within the secondbrake caliper 642. The second brake caliper 642 and the plurality ofsecond brake pads 644 may be any type of brake caliper and brake padsknown to those with ordinary skill in the art.

The second hub assembly 650 is shown in FIGS. 23 and 24 and includes asecond hub housing 652, a second spindle 654, a second inner hub bearing656, a second outer hub bearing 658, a second hub ring 660, and a secondhub retainer 662.

The second hub housing 652, as shown in FIG. 24, has a circular secondhub housing base 652 a and a hollow, cylindrical second hub housing body652 extending from a side of the second hub housing base 652 a.

The second spindle 654, as shown in FIG. 24, is a substantially tubularmember having a second spindle end 654 a at a first end and a secondspindle securing end 654 e at an opposite second end. The second spindlesecuring end 654 e may have an exterior thread. The second spindle 654also has a second spindle groove 654 b, a second spindle ridge 654 c,and a second outer spindle surface 654 d disposed between the first endand the second end. The second spindle groove 654 b is a grooveextending circumferentially around the second spindle 654 adjacent thefirst end. The second spindle ridge 654 c protrudes circumferentiallyaround the second spindle 654 and is disposed between the second spindlegroove 654 b and the second spindle securing end 654 e.

The second outer spindle surface 654 d is a flat surface formedorthogonal to a longitudinal direction of the second spindle 654 andextending circumferentially around the second spindle 654. The secondouter spindle surface 654 d is disposed between the second spindle ridge654 c and the second spindle securing end 654 e.

The second inner hub bearing 656 and the second outer hub bearing 658may be any form of bearing known to those with ordinary skill in theart. The second hub ring 660 is a circular member. The second hubretainer 662 may be a threaded nut, or may be any other form of retainerknown to those with ordinary skill in the art.

The second drive shaft 670 is shown in FIG. 23 and has a second driveshaft flange 672 disposed on a first end and a second drive shaft spline676 disposed on an opposite second end. A second drive shaft body 674 isa cylindrical member extending between the second drive shaft flange 672and the second drive shaft spline 676.

The second rotor actuator assembly 680 is shown in FIG. 25 has a secondrotor actuator 682, a plurality of second rotor actuator bearings 690,and a second rotor actuator snap ring 692. The second rotor actuator 682has a plurality of second rotor actuator teeth 684 disposed on a firstend, a second rotor actuator mating end 686 at an opposite second end,and a second rotor actuator spline 688 disposed along an interior of thesecond rotor actuator 682. The plurality of second rotor actuator teeth684 protrude from the second rotor actuator 682 in a longitudinaldirection of the second rotor actuator 682. The second rotor actuatorspline 688 extends along the longitudinal direction of the second rotoractuator 682. The second rotor actuator mating end 686 may have anexterior thread. The plurality of second rotor actuator bearings 690 maybe any type of bearings known to those with ordinary skill in the art.The second actuator snap ring 692 may be any type of snap ring known tothose with ordinary skill in the art.

The engagement assembly 700 is shown in FIGS. 2, 6, and 10. Theengagement assembly 700 includes a main shaft 710, a pivot coupling 720,a first lever assembly 730, and a second lever assembly 760.

As shown in FIG. 2, the main shaft 710 is an elongated cylindricalmember. The pivot coupling 720 has a first pivot arm 722, a second pivotarm 724, and a plurality of pivot bases 726. In the shown embodiment,the first pivot arm 722 and the second pivot arm 724 are L-shapedmembers, and the plurality of pivot bases 726 are formed as tabs.

The first lever assembly 730 is shown in FIGS. 2, 6, and 10. The firstlever assembly 730 has a first pivot rod 732, a first engagement lever734, a first lever seal 736, a first lever upper snap ring 738, a firstlever upper bearing 740, a first engagement shaft 742, a first leverlower bearing 744, a first lever lower snap ring 746, and a firstactuator pivot assembly 750.

The first pivot rod 732, as shown in FIG. 2, is an elongated cylindricalmember. The first engagement lever 734 has a first engagement leverprotrusion 734 a at an end. The first engagement lever protrusion 734 ais a tubular member extending from the first engagement lever 734, andhas a first engagement lever spline 734 b disposed along an interior.

The first lever seal 736 may be a circular rubber seal or any other typeof seal known to those with ordinary skill in the art. The first leverupper snap ring 738 and the first lever lower snap ring 746 may be anytype of snap ring known to those with ordinary skill in the art. Thefirst lever upper bearing 740 and the first lever lower bearing 744 maybe any type of bearing known to those with ordinary skill in the art.

The first engagement shaft 742, as shown in FIG. 10, is a tubular memberhaving a first engagement shaft spline 742 a at a first end and a firstengagement shaft grommet 742 d at an opposite second end. The firstengagement shaft spline 742 a extends along a longitudinal direction ofthe first engagement shaft 742. The first engagement shaft grommet 742 dprotrudes circumferentially around the first engagement shaft 742. Thefirst engagement shaft 742 also has a first engagement shaft uppersurface 742 b and a first engagement shaft lower surface 742 c disposedbetween the first end and the second end. The first engagement shaftupper surface 742 b extends circumferentially around the firstengagement shaft 742 and perpendicularly to the first engagement shaft742 adjacent the first end. The first engagement shaft lower surface 742c extends circumferentially around the first engagement shaft 742 andperpendicularly to the first engagement shaft 742, and is disposedadjacent the first engagement shaft grommet 742 d. The first engagementshaft 742 also has a plurality of first engagement shaft keyways 742 eformed as indentations extending into the first engagement shaft 742between the first engagement shaft upper surface 742 b and the firstengagement shaft lower surface 742 c.

The first actuator pivot assembly 750 is shown in FIGS. 6 and 10. Thefirst actuator pivot assembly 750 includes a first yoke 752, a pluralityof first yoke keys 754, a first upper actuator collar 756, and a firstlower actuator collar 758. The first yoke 752 is a U-shaped memberhaving a pair of first yoke arms 752 a extending in parallel fromopposite ends of a first yoke body 752 b. The plurality of first yokekeys 754 are disposed within the first yoke body 752 b. The first upperactuator collar 756 and the first lower actuator collar 758, shown inFIG. 6, are U-shaped members. The first upper actuator collar 756 has acylindrical first upper actuator collar protrusion 756 a extending froman approximate center of the first upper actuator collar 756. The firstlower actuator collar 758 has a cylindrical first lower actuator collarprotrusion 758 a extending from an approximate center of the first loweractuator collar 758.

The second lever assembly 760 is shown in FIGS. 2, 22, and 26. Thesecond lever assembly 760 has a second pivot rod 762, a secondengagement lever 764, a second lever seal 766, a second lever upper snapring 768, a second lever upper bearing 770, a second engagement shaft772, a second lever lower bearing 774, a second lever lower snap ring776, and a second actuator pivot assembly 780.

The second pivot rod 762, as shown in FIG. 2, is an elongatedcylindrical member. The second engagement lever 764 has a secondengagement lever protrusion 764 a at an end. The second engagement leverprotrusion 764 a is a tubular member extending from the secondengagement lever 764, and has a second engagement lever spline 764 bdisposed along an interior.

The second lever seal 766 may be a circular rubber seal or any othertype of seal known to those with ordinary skill in the art. The secondlever upper snap ring 768 and the second lever lower snap ring 776 maybe any type of snap ring known to those with ordinary skill in the art.

The second lever upper bearing 770 and the second lever lower bearing774 may be any type of bearing known to those with ordinary skill in theart.

The second engagement shaft 772, as shown in FIG. 26, is a tubularmember having a second engagement shaft spline 772 a at a first end anda second engagement shaft grommet 772 d at an opposite second end. Thesecond engagement shaft spline 772 a extends along a longitudinaldirection of the second engagement shaft 772. The second engagementshaft grommet 772 d protrudes circumferentially around the secondengagement shaft 772. The second engagement shaft 772 also has a secondengagement shaft upper surface 772 b and a second engagement shaft lowersurface 772 c disposed between the first end and the second end. Thesecond engagement shaft upper surface 772 b extend circumferentiallyaround the second engagement shaft 772 and perpendicularly to the secondengagement shaft 772 adjacent the first end. The second engagement shaftlower surface 772 c extends circumferentially around the secondengagement shaft 772 and perpendicularly to the second engagement shaft772, and is disposed adjacent the second engagement shaft grommet 772 d.The second engagement shaft 772 also has a plurality of secondengagement shaft keyways 772 e formed as indentations extending into thesecond engagement shaft 772 between the second engagement shaft uppersurface 772 b and the second engagement shaft lower surface 772 c.

The second actuator pivot assembly 780 is shown in FIGS. 22 and 26includes a second yoke 782, a plurality of second yoke keys 784, asecond upper actuator collar 786, and a second lower actuator collar788. The second yoke 782 is a U-shaped member having a pair of secondyoke arms 782 a extending in parallel from opposite ends of a secondyoke body 782 b. The plurality of second yoke keys 784 are disposedwithin the second yoke body 782 b. The second upper actuator collar 786and the second lower actuator collar 788, shown in FIG. 22, are U-shapedmembers. The second upper actuator collar 786 has a cylindrical secondupper actuator collar protrusion 786 a extending from an approximatecenter of the second upper actuator collar 786. The second loweractuator collar 788 has a cylindrical second lower actuator collarprotrusion 788 a extending from an approximate center of the secondlower actuator collar 788.

Assembly of the hydraulic drive system 1 according to an exemplaryembodiment of the invention will now be described in greater detail withreference to FIGS. 2-13.

As shown in FIGS. 2 and 3, the plurality of first exterior lines 210extend from outside the body housing 100 to the plurality of fluid lineports 130. The plurality of first wall connectors 214 are positioned inthe plurality of fluid line ports 130 and connect the plurality of firstexterior lines 210 with the first interior line 220 and the secondinterior line 222 positioned inside the body housing 100.

The first motor assembly 300, as shown in FIGS. 3-5, is positionedinside the body housing 100. As shown in FIGS. 3 and 4, the firstinterior coupling 240 connects the first interior line 220 to the firstmotor coupling 314, and the second interior coupling 242 connects thesecond interior line 222 to the first motor coupling 312. As shown inFIGS. 3, 5, and 11, a plurality of fasteners 800 attach the first motor310 to a first side of the first planetary gear drive 330. The firstmotor shaft 316 extends into the first planetary gear drive 330, and issurrounded by the first motor adaptor 320, which permits the first motor310 to engage with and operate the first planetary gear drive 330. Thefirst motor actuator 340 is disposed in an opposite second side of thefirst planetary gear drive 330, with the first motor actuator matingspline 342 mating with the first planetary mating spline 332. Due to themating of the first motor actuator mating spline 342 and the firstplanetary mating spline 332, the first motor actuator 340 is movablewith respect to the first planetary gear drive 330 in a direction of thelongitudinal axis of the first motor actuator 340.

As shown in FIGS. 4, 5 and 11, a plurality of fasteners 800 attach thesecond side of the first planetary gear drive 330 to the first bellhousing flange 512. The first motor actuator 340 and a portion of thefirst planetary gear drive 330 are disposed in the first bell housingreceiving space 511. The body housing 100, as shown in FIGS. 4 and 11,is also attached to the first bell housing flange 512 by a plurality offasteners 800, with the body housing 100 positioned around the firstplanetary gear drive 330 and containing the first motor assembly 300.[0095] The first rotor actuator 582 is disposed in the first bellhousing receiving space 511, as shown in FIGS. 9 and 11, with the firstrotor actuator teeth 584 facing the first motor actuator teeth 346. Theplurality of first rotor actuator bearings 590 are secured to the firstrotor actuator 582 by the first rotor actuator snap ring 592. The firstrotor actuator 582 is secured to the first bell housing 510 within thefirst bell housing receiving space 511 by the plurality of first rotoractuator bearings 590, and the first rotor actuator 582 is rotatablewithin the plurality of first rotor actuator bearings 590 and withrespect to the first bell housing 510.

The first hub assembly 550 is assembled with the first rotor assembly500 as shown in FIGS. 8 and 11. The first spindle end 554 a and thefirst spindle groove 554 b are disposed within the first caster housing516, with the first spindle ridge 554 c abutting an end of the firstcaster housing 516. A plurality of fasteners 800 extend through thefirst caster housing 516, abutting the first caster housing 516 anddisposed within each first spindle groove 554 b to secure the firstspindle 554 with respect to the first caster housing 516. The firstouter spindle surface 554 d and the first spindle securing end 554 e aredisposed outside of the first caster housing 516. The first inner hubbearing 556 is positioned around the first spindle 554 and abuts thefirst outer spindle surface 554 d. The first hub housing base 552 a isdisposed around and abuts the first inner hub bearing 556. The firstouter hub bearing 558 is positioned around the first spindle 554adjacent the second end and is disposed between the first hub housingbody 552 b and the first spindle 554. The first outer hub bearing 558 issecured to the first spindle 554 by the first hub ring 560 and the firsthub retainer 562 mating with the first spindle securing end 554 e. Dueto both the first inner hub bearing 556 and the first outer hub bearing558 being disposed between the first hub housing 552 and the firstspindle 554, the first hub housing 552 is rotatable with respect to thefirst spindle 554.

As shown in FIGS. 7 and 11, the first rotor 530 is attached to the firsthub housing base 552 a by a plurality of fasteners 800. The first rotor530 is thus also rotatable with respect to the first spindle 554. Thefirst brake 540 is disposed on the first rotor 530 with the first brakepads 544 adjacent the first rotor 530 on each side of the first rotor530 and the first brake caliper 542 disposed around the first brake pads544. A side of the first brake caliper 542 is attached at each end tothe first brake mount 520. The first brake 540 is secured to the firstcaster housing 516 and the first rotor 530 can rotate within the firstbrake 540.

The first drive shaft flange 572 is attached to the first hub housingbody 552 b by a plurality of fasteners 800, as shown in FIGS. 7 and 11,and the first drive shaft body 574 extends through the first spindle554. The first drive shaft spline 576 mates with the first rotoractuator spline 588 such that the first drive shaft 570, the first hubhousing 552, and the first rotor 530 rotate with the first rotoractuator 582.

As shown in FIG. 2, the main shaft 710 is positioned outside of the bodyhousing 100 and attached along a first end to a first end of the firstpivot arm 722 and a first end of the second pivot arm 724. The pluralityof pivot bases 726 are attached to an exterior of the body housing 100,and a center of each of the first pivot arm 722 and the second pivot arm724 is pivotably attached to one of the plurality of pivot bases 726 bya fastener 800.

An opposite second end of the first pivot arm 722, as shown in FIG. 2,is pivotably attached to the first pivot rod 732 which extends outsideof the body housing 100 from the first pivot arm 722 to the firstengagement lever 734. The first pivot rod 732 is attached to an end ofthe first engagement lever 734 opposite the first engagement leverprotrusion 734 a. The first engagement lever 734 is disposed on thefirst bell housing 510 with the first engagement lever protrusion 734 adisposed over the first shaft receiving passageway 514.

As shown in FIGS. 10 and 12, the first engagement shaft 742 extendsthrough the first shaft receiving passageway 514. The first engagementshaft spline 742 a engages with the first engagement lever spline 734 bsuch that motion of the first engagement lever 734 imparts motion to thefirst engagement shaft 742. The first lever seal 736 is disposed withinthe first lever upper snap ring 738 and positioned around the firstengagement shaft 742 outside the first bell housing 510. The first leverupper bearing 740 is disposed around the first engagement shaft 742 andseated within the first shaft receiving passageway 514. The first leverupper bearing 740 also abuts the first engagement shaft upper surface742 b. The second end of the first engagement shaft 742 extends out ofthe first shaft receiving passageway 514. The first lever lower bearing744 is disposed around the first engagement shaft 742 and is held on thefirst engagement shaft 742 by the first engagement shaft grommet 742 d.The first lever lower bearing 744 is seated in the first shaft receivingpassageway 514 and also abuts the first engagement shaft lower surface742 c. Due to the first lever upper bearing 740 and the first leverlower bearing 744, the first engagement shaft 742 is rotatable withrespect to the first bell housing 510. The first lever lower snap ring746 is disposed in the end of the first shaft receiving passageway 514adjacent the second end of the first engagement shaft 742.

As shown in FIGS. 6, 10, 12, and 13, the first actuator pivot assembly750 is attached to the first engagement shaft 742 within the first bellhousing receiving space 511. The first yoke body 752 b is disposedaround the first engagement shaft 742 and secured by a plurality offasteners 800. The plurality of first yoke keys 754 each engage one ofthe plurality of first engagement shaft keyways 742 e, fixing the firstyoke 752 with respect to the first engagement shaft 742. The first upperactuator collar protrusion 756 a is rotatably connected to an end of oneof the pair of first yoke arms 752 a and the first lower actuator collarprotrusion 758 a is rotatably connected to an end of the other of thepair of first yoke arms 752 a. The first upper actuator collar 756 andthe first lower actuator collar 758 each engage the plurality of firstmotor actuator ridges 344 on a side of the first motor actuator 340, anda plurality of fasteners 800 connect the first upper actuator collar 756to the first lower actuator collar 758, fixing the first motor actuator340 between the first upper actuator collar 756 and the first loweractuator collar 758. The first motor actuator 340 is thus disposedwithin the first planetary gear drive 330 and also attached to the firstactuator pivot assembly 750.

As shown in FIGS. 2, 19, 30 and 31, the plurality of second exteriorlines 212 extend from outside the body housing 100 to the plurality offluid line ports 130. The plurality of second wall connectors 216 arepositioned in the plurality of fluid line ports 130 and connect theplurality of second exterior lines 212 with the third interior line 230and the fourth interior line 232 positioned inside the body housing 100.

The second motor assembly 400, as shown in FIGS. 19-21, is positionedinside the body housing 100. As shown in FIGS. 19 and 20, the thirdinterior coupling 250 connects the third interior line 230 to the secondmotor coupling 414, and the fourth interior coupling 252 connects thefourth interior line 232 to the second motor coupling 412. As shown inFIGS. 19, 21, and 27, a plurality of fasteners 800 attach the secondmotor 410 to a first side of the second planetary gear drive 430. Thesecond motor shaft 416 extends into the second planetary gear drive 430,and is surrounded by the second motor adaptor 420, which permits thesecond motor 410 to engage with and operate the second planetary geardrive 430. The second motor actuator 440 is disposed in an oppositesecond side of the second planetary gear drive 430, with the secondmotor actuator mating spline 442 mating with the second planetary matingspline 432. Due to the mating of the second motor actuator mating spline442 and the second planetary mating spline 432, the second motoractuator 440 is movable with respect to the second planetary gear drive430 in a direction of the longitudinal axis of the second motor actuator440.

As shown in FIGS. 20, 21 and 27, a plurality of fasteners 800 attach thesecond side of the second planetary gear drive 430 to the second bellhousing flange 612. The second motor actuator 440 and a portion of thesecond planetary gear drive 430 are disposed in the second bell housingreceiving space 611. The body housing 100, as shown in FIGS. 20 and 27,is also attached to the second bell housing flange 612 by a plurality offasteners 800, with the body housing 100 positioned around the secondplanetary gear drive 430 and containing the second motor assembly 400.

The second rotor actuator 682 is disposed in the second bell housingreceiving space 611, as shown in FIGS. 25 and 27, with the second rotoractuator teeth 684 facing the second motor actuator teeth 446. Theplurality of second rotor actuator bearings 690 are secured to thesecond rotor actuator 682 by the second rotor actuator snap ring 692.The second rotor actuator 682 is secured to the second bell housing 610within the second bell housing receiving space 611 by the plurality ofsecond rotor actuator bearings 690, and the second rotor actuator 682 isrotatable within the plurality of second rotor actuator bearings 690 andwith respect to the second bell housing 610.

The second hub assembly 650 is assembled with the second rotor assembly600 as shown in FIGS. 24 and 27. The second spindle end 654 a and thesecond spindle groove 654 b are disposed within the second casterhousing 616, with the second spindle ridge 654 c abutting an end of thesecond caster housing 616. A plurality of fasteners 800 extend throughthe second caster housing 616, abutting the second caster housing 616and disposed within each second spindle groove 654 b to secure thesecond spindle 654 with respect to the second caster housing 616. Thesecond outer spindle surface 654 d and the second spindle securing end654 e are disposed outside of the second caster housing 616. The secondinner hub bearing 656 is positioned around the second spindle 654 andabuts the second outer spindle surface 654 d. The second hub housingbase 652 a is disposed around and abuts the second inner hub bearing656. The second outer hub bearing 658 is positioned around the secondspindle 654 adjacent the second end and is disposed between the secondhub housing body 652 b and the second spindle 654. The second outer hubbearing 658 is secured to the second spindle 654 by the second hub ring660 and the second hub retainer 662 mating with the second spindlesecuring end 654 e. Due to both the second inner hub bearing 656 and thesecond outer hub bearing 658 being disposed between the second hubhousing 652 and the second spindle 654, the second hub housing 652 isrotatable with respect to the second spindle 654.

As shown in FIGS. 23 and 27, the second rotor 630 is attached to thesecond hub housing base 652 a by a plurality of fasteners 800. Thesecond rotor 630 is thus also rotatable with respect to the secondspindle 654. The second brake 640 is disposed on the second rotor 630with the second brake pads 644 adjacent the second rotor 630 on eachside of the second rotor 630 and the second brake caliper 642 disposedaround the second brake pads 644. A side of the second brake caliper 642is attached at each end to the second brake mount 620. The second brake640 is secured to the second caster housing 616 and the second rotor 630can rotate within the second brake 640.

The second drive shaft flange 672 is attached to the second hub housingbody 652 b by a plurality of fasteners 800, as shown in FIGS. 23 and 27,and the second drive shaft body 674 extends through the second spindle654. The second drive shaft spline 676 mates with the second rotoractuator spline 688 such that the second drive shaft 670, the second hubhousing 652, and the second rotor 630 rotate with the second rotoractuator 682.

An opposite second end of the second pivot arm 724, as shown in FIG. 2,is pivotably attached to the second pivot rod 762 which extends outsideof the body housing 100 from the second pivot arm 724 to the secondengagement lever 764. The second pivot rod 762 is attached to an end ofthe second engagement lever 764 opposite the second engagement leverprotrusion 764 a. The second engagement lever 764 is disposed on thesecond bell housing 610 with the second engagement lever protrusion 764a disposed over the second shaft receiving passageway 614.

As shown in FIGS. 26 and 28, the second engagement shaft 772 extendsthrough the second shaft receiving passageway 614. The second engagementshaft spline 772 a engages with the second engagement lever spline 764 bsuch that motion of the second engagement lever 764 imparts motion tothe second engagement shaft 772. The second lever seal 766 is disposedwithin the second lever upper snap ring 768 and positioned around thesecond engagement shaft 772 outside the second bell housing 610. Thesecond lever upper bearing 770 is disposed around the second engagementshaft 772 and seated within the second shaft receiving passageway 614.The second lever upper bearing 770 also abuts the second engagementshaft upper surface 772 b. The second end of the second engagement shaft772 extends out of the second shaft receiving passageway 614. The secondlever lower bearing 774 is disposed around the second engagement shaft772 and is held on the second engagement shaft 772 by the secondengagement shaft grommet 772 d. The second lever lower bearing 774 isseated in the second shaft receiving passageway 614 and also abuts thesecond engagement shaft lower surface 772 c. Due to the second leverupper bearing 770 and the second lever lower bearing 774, the secondengagement shaft 772 is rotatable with respect to the second bellhousing 610. The second lever lower snap ring 776 is disposed in the endof the second shaft receiving passageway 614 adjacent the second end ofthe second engagement shaft 772.

As shown in FIGS. 22, 26, 28, and 29, the second actuator pivot assembly780 is attached to the second engagement shaft 772 within the secondbell housing receiving space 611. The second yoke body 782 b is disposedaround the second engagement shaft 772 and secured by a plurality offasteners 800. The plurality of second yoke keys 784 each engage one ofthe plurality of second engagement shaft keyways 772 e, fixing thesecond yoke 782 with respect to the second engagement shaft 772. Thesecond upper actuator collar protrusion 786 a is rotatably connected toan end of one of the pair of second yoke arms 782 a and the second loweractuator collar protrusion 788 a is rotatably connected to an end of theother of the pair of second yoke arms 782 a. The second upper actuatorcollar 786 and the second lower actuator collar 788 each engage theplurality of second motor actuator ridges 444 on a side of the secondmotor actuator 440, and a plurality of fasteners 800 connect the secondupper actuator collar 786 to the second lower actuator collar 788,fixing the second motor actuator 440 between the second upper actuatorcollar 786 and the second lower actuator collar 788. The second motoractuator 440 is thus disposed within the second planetary gear drive 430and also attached to the second actuator pivot assembly 780.

An exemplary assembly of a hydraulic drive system 1 according to theinvention with trailer 900 will now be described in greater detail withreference to FIG. 1.

The frame 910 is a rigid structure formed from a plurality of beams 914.The frame 910 has a hitch 912 disposed at a first end. The hitch 912includes a connector, for example, a ball mount, for connecting theframe 910 with a towing device (not shown). The pair of steerable wheels950 are both positioned under and pivotably attached to the frame 910adjacent the first end.

The hydraulic drive system 1 is attached to an underside of the frame910 adjacent an opposite second end of the frame 910. The hydraulicdrive system 1 extends orthogonally with respect to a longitudinal axisof the frame 910. Each of the pair of drive wheels 940 is attached toone of the first rotor 530 and the second rotor 630. The pair of drivewheels 940 and the pair of steerable wheels 950 together support theframe 910 and components attached to the frame 910.

The fluid supply system 920 supplies hydraulic fluid to the hydraulicdrive system 1. The fluid supply system 920 has a pump 922 and a fluidreservoir 924 each attached to the frame 910. The fluid reservoir 924stores hydraulic fluid. The pump 922 is connected to the plurality offirst exterior lines 210 and the plurality of second exterior lines 212and pumps hydraulic fluid from the fluid reservoir 924 through the fluidline assembly 200. The pump 922 is capable of pumping hydraulic fluidthrough the fluid line assembly 200 in either a first direction or anopposite second direction.

The engagement mechanism 930 is attached to an underside of the frame910. The engagement mechanism 930 is connected to the hitch 912 at afirst end and the main shaft 710 at an opposite second end. Theengagement mechanism 930 moves the main shaft 710 in a longitudinaldirection of the main shaft 710 based on whether the hitch 912 isattached to the towing device.

The use of the hydraulic drive system 1 within the exemplary trailer 900will now be described in greater detail with reference to FIGS. 1, 3,11, and 13-18. The hydraulic drive system 1 is used to drive the pair ofdrive wheels 940 to more precisely locate the trailer 900 when thetrailer 900 is not being towed.

The plurality of first motor actuator teeth 346, as shown in FIGS.16-18, are matable with the plurality of first rotor actuator teeth 584.The plurality of second motor actuator teeth 446, as shown in FIGS.32-34, are matable with the plurality of second rotor actuator teeth684. The engagement assembly 700, as described in greater detail below,moves the first motor actuator 340 with respect to the first rotoractuator 582 between an engagement position in which the first motoractuator 340 mates with and engages the first rotor actuator 582 and adisengagement position in which the first motor actuator 340 and thefirst rotor actuator 582 are separated. The engagement assembly 700likewise moves the second motor actuator 440 with respect to the secondrotor actuator 682 between the engagement position in which the secondmotor actuator 440 mates with and engages the second rotor actuator 682and the disengagement position in which the second motor actuator 440and the second rotor actuator 682 are separated.

The engagement position of the hydraulic drive system 1 is shown inFIGS. 14 and 17. As shown in FIGS. 1 and 14, when the hitch 912 is notattached to the towing device, the engagement mechanism 930 does notaffect the main shaft 710, and the main shaft 710 is positioned closerto the body housing 100.

In the engagement position, the first pivot rod 732 is positioned closerto the main shaft 710, pulling the first engagement lever 734 toward thehousing body 100. As the first engagement lever 734 is pulled toward thehousing body 100, as shown in FIGS. 13 and 17, the first yoke 752 turnswith the first engagement shaft 742 and moves the first motor actuator340 toward the first rotor actuator 582 in a longitudinal direction ofthe first motor actuator 340. As shown in FIG. 17, the first motoractuator 340 is moved until the plurality of first motor actuator teeth346 engage with the plurality of first rotor actuator teeth 584. Aportion of the first motor actuator 340 remains within the firstplanetary gear drive 330 as the first motor actuator mating spline 342slides along the first planetary mating spline 332 during motion of thefirst motor actuator 340.

The hydraulic drive system 1 only provides motive power to the pair ofdrive wheels 940 in the engagement position in which the plurality offirst motor actuator teeth 346 are engaged with the plurality of firstrotor actuator teeth 584. In the engagement position, rotation of thefirst motor actuator 340 imparts rotation to the first rotor actuator582. The pump 922 pumps hydraulic fluid from the fluid reservoir 924through the plurality of first exterior lines 210 and through each ofthe first interior line 220 and the second interior line 222, as shownin FIGS. 3 and 14. Depending on the direction of fluid flow created bythe pump 922, one of the first interior line 220 and the second interiorline 222 is an input line, and the other of the first interior line 220and the second interior line 222 is an output line.

The first interior line 220 and the second interior line 222 transmithydraulic fluid to operate the first motor 310, which operates the firstplanetary gear drive 330. Rotation of the first planetary gear drive 330rotates the first motor actuator 340 via the interaction of the firstplanetary mating spline 332 and the first motor actuator mating spline342. In the engagement position shown in FIG. 17, rotation of the firstmotor actuator 340 imparts rotation to the first rotor actuator 582. Asshown in FIG. 11, rotation of the first rotor actuator 582 rotates thefirst drive shaft 570 via the interaction of the first rotor actuatorspline 588 and the first drive shaft spline 576. The first drive shaft570 is fixed to the first hub housing 552 and the first hub housing 552is fixed to the first rotor 530, and consequently, rotation of the firstdrive shaft 570 imparts rotation to the first rotor 530, providingmotive power to one of the pair of drive wheels 940. If, for example,the first interior line 220 is the input line, the first motor 310imparts a rotation that turns the drive wheel 940 in a clockwisedirection, and if the first interior line 220 is the output line, thefirst motor 310 imparts a rotation that turns the drive wheel 940 in acounterclockwise direction.

A similar engagement occurs on the symmetrical other side of thehydraulic drive system 1. In the engagement position, as shown in FIGS.14 and 30, the second pivot rod 762 is positioned closer to the mainshaft 710, pulling the second engagement lever 764 toward the housingbody 100. As the second engagement lever 764 is pulled toward thehousing body 100, as shown in FIGS. 29 and 33, the second yoke 782 turnswith the second engagement shaft 772 and moves the second motor actuator440 toward the second rotor actuator 682 in a longitudinal direction ofthe second motor actuator 440. The second motor actuator 440 is moveduntil the plurality of second motor actuator teeth 446 engage with theplurality of second rotor actuator teeth 684. A portion of the secondmotor actuator 440 remains within the second planetary gear drive 430 asthe second motor actuator mating spline 442 slides along the secondplanetary mating spline 432 during motion of the second motor actuator440.

The hydraulic drive system 1 only provides motive power to the pair ofdrive wheels 940 in the engagement position in which the plurality ofsecond motor actuator teeth 446 are engaged with the plurality of secondrotor actuator teeth 684. In the engagement position, rotation of thesecond motor actuator 440 imparts rotation to the second rotor actuator682. The pump 922 pumps hydraulic fluid from the fluid reservoir 924through the plurality of second exterior lines 212 and through each ofthe third interior line 230 and the fourth interior line 232, as shownin FIGS. 19 and 30. Depending on the direction of fluid flow created bythe pump 922, one of the third interior line 230 and the fourth interiorline 232 is an input line, and the other of the third interior line 230and the fourth interior line 232 is an output line.

The third interior line 230 and the fourth interior line 232 providehydraulic fluid to operate the second motor 410, which operates thesecond planetary gear drive 430. Rotation of the second planetary geardrive 430 rotates the second motor actuator 440 via the interaction ofthe second planetary mating spline 432 and the second motor actuatormating spline 442. In the engagement position shown in FIG. 33, rotationof the second motor actuator 440 imparts rotation to the second rotoractuator 682. As shown in FIG. 27, rotation of the second rotor actuator682 rotates the second drive shaft 670 via the interaction of the secondrotor actuator spline 688 and the second drive shaft spline 676. Thesecond drive shaft 670 is fixed to the second hub housing 652 and thesecond hub housing 652 is fixed to the second rotor 630, andconsequently, rotation of the second drive shaft 670 imparts rotation tothe second rotor 630, providing motive power to one of the pair of drivewheels 940. If, for example, the third interior line 230 is the inputline, the second motor 410 imparts a rotation that turns the drive wheel940 in a clockwise direction, and if the third interior line 230 is theoutput line, the second motor 410 imparts a rotation that turns thedrive wheel 940 in a counterclockwise direction.

Consequently, when the trailer 900 is not attached to the towing device,the engagement assembly 700 automatically moves to the engagementposition in which rotation of either the first motor 310 or the secondmotor 410 imparts rotation to the pair of drive wheels 940, allowing thehydraulic drive system 1 to drive the trailer 900.

The disengagement position of the hydraulic drive system 1 is shown inFIGS. 15 and 18. As shown in FIG. 15, when the hitch 912 is attached tothe towing device, the engagement mechanism 930 pulls the main shaft 710in a direction away from the body housing 100 along the longitudinalaxis of the main shaft 710.

When the main shaft 710 is positioned further from the body housing 100,the first pivot rod 732 is positioned further from the main shaft 710,pushing the first engagement lever 734 in a direction away from thehousing body 100. As the first engagement lever 734 is pushed away fromthe housing body 100, as shown in FIGS. 13 and 18, the first yoke 752turns with the first engagement shaft 742 and moves the first motoractuator 340 away from the first rotor actuator 582 in the longitudinaldirection of the first motor actuator 340. As shown in FIG. 18, thefirst motor actuator 340 is moved until the plurality of first motoractuator teeth 346 disengage from the plurality of first rotor actuatorteeth 584. In the disengagement position, the plurality of first motoractuator teeth 346 are separated from and face the plurality of firstrotor actuator teeth 584.

A similar disengagement occurs on the symmetrical other side of thehydraulic drive system 1. As shown in FIGS. 15, 31, and 34 when the mainshaft 710 is positioned further from the body housing 100, the secondpivot rod 762 is positioned further from the main shaft 710, pushing thesecond engagement lever 764 in a direction away from the housing body100. As the second engagement lever 764 is pushed away from the housingbody 100, the second yoke 782 turns with the second engagement shaft 772and moves the second motor actuator 440 away from the second rotoractuator 682 in the longitudinal direction of the second motor actuator440 until the plurality of second motor actuator teeth 446 disengagefrom the plurality of second rotor actuator teeth 684. In thedisengagement position, the plurality of second motor actuator teeth 446are separated from and face the plurality of second rotor actuator teeth684.

Consequently, when the trailer 900 is attached to the towing device, theengagement assembly 700 automatically moves to the disengagementposition in which rotation of either the first motor 310 or the secondmotor 410 does not impart rotation to any portion of the first or secondrotor assemblies 500, 600. The pair of drive wheels 940 thus roll freelywithout impairment from the first motor 310 or the second motor 410 whenthe hydraulic drive system 1 is not needed to drive the pair of drivewheels 940.

The foregoing illustrates some of the possibilities for practicing theinvention. Many other embodiments are possible within the scope andspirit of the invention. The disclosed invention utilizes the aboveidentified components, as a system, in order to more efficientlyconstruct a hydraulic drive system 1 for a particular purpose.Therefore, more or less of the aforementioned components can be used toconform to that particular purpose. It is, therefore, intended that theforegoing description be regarded as illustrative rather than limiting,and that the scope of the invention is given by the appended claimstogether with their full range of equivalents.

What is claimed is:
 1. A trailer, comprising: a frame with a pair ofdrive wheels positioned on opposite sides thereof; and a hydraulic drivesystem attached to an underside of the frame, the hydraulic drive systemhaving: a first rotor assembly arranged along a first side of the frameand having a first rotor and a first drive shaft extending through andconnectable with the first rotor; a first motor assembly disposed alongthe first side of the frame and positioned linearly the first rotorassembly and having a first motor actuator; a first lever assembly toreversibly engage and disengage the motor actuator with the first driveshaft; a first drive wheel of the pair of drive wheels connected to thefirst rotor; a second rotor assembly arranged along a second side of theframe that is opposite the first side and having a second rotor and asecond drive shaft extending through and connectable with the secondrotor; a second motor assembly disposed along the second side of theframe and positioned linearly the second rotor assembly and having asecond motor actuator; a second lever assembly to reversibly engage anddisengage the motor actuator with the first drive shaft, the secondlever assembly independent of the first lever assembly; and a seconddrive wheel of the pair of drive wheels connected to the second rotor.2. The trailer of claim 1, further comprising an engagement assemblymoving the first motor actuator toward and away from the first rotorassembly to respectively engage and disengage therewith and moving thesecond motor actuator toward and away from the second rotor assembly torespectively engage and disengage therewith.
 3. The trailer of claim 1,wherein the first motor actuator includes a plurality of motor actuatorteeth disposed on an end thereof.
 4. The trailer of claim 3, wherein thefirst rotor actuator includes a plurality of rotor actuator teethdisposed on an end.
 5. The trailer of claim 4, wherein the plurality ofmotor actuator teeth correspond with and separated from the plurality ofrotor actuator teeth when positioned in a disengagement position.
 6. Thetrailer of claim 5, wherein the plurality of motor actuator teethcorrespond with and engage the plurality of rotor actuator teeth whenpositioned in an engagement position.
 7. The trailer of claim 1, whereinthe first hydraulic motor is connected to a planetary gear drive by amotor shaft extends from the hydraulic motor and into the planetary geardrive.
 8. The trailer of claim 7, wherein the first hydraulic motoroperates the planetary gear drive.
 9. The trailer of claim 8, whereinthe first motor actuator is positioned on an opposite side of theplanetary gear drive with respect to the hydraulic motor.
 10. Thetrailer of claim 9, wherein the first rotor actuator is positioned in abell housing of the first rotor assembly.
 11. The trailer of claim 10,wherein the first rotor actuator includes a rotor actuator splineengaged with the first drive shaft such that rotation of the first rotoractuator imparts rotation to the first drive shaft.
 12. The trailer ofclaim 11, wherein the first drive shaft is secured to a hub housingfixed to the first rotor.